Methods and apparatus for treating body tissue sphincters and the like

ABSTRACT

A plurality of structures that resiliently attract one another are provided for implanting in a patient around a body tissue structure of the patient. For example, the body tissue structure may be the esophagus, and the plurality of structures may be implanted in an annulus around the outside of the esophagus, the annulus being substantially coaxial with the esophagus. The attraction may be between annularly adjacent ones of the structures in the annulus, and it may be provided, for example, by magnets or springs. The array of structures is preferably self-limiting with respect to the smallest area that it can encompass, and this smallest area is preferably large enough to prevent the apparatus from applying excessive pressure to tissue passing through that area.

This application claims the benefit of U.S. provisional patentapplications 60/599,333, filed Aug. 5, 2004; 60/614,835, filed Sep. 30,2004; and 60/653,966, filed Feb. 17, 2005, all of which are herebyincorporated by reference herein in their entireties.

This is a continuation of U.S. patent application Ser. No. 11/147,801,filed Jun. 7, 2005, which is a continuation-in-part of U.S. patentapplication Ser. Nos. 10/134,306, filed Apr. 26, 2002; 10/732,696, filedDec. 9, 2003; 10/732,693, filed Dec. 9, 2003; 10/612,496, filed Jul. 1,2003; 10/802,992, filed Mar. 16, 2004; and 11/059,173, filed Feb. 16,2005, all of which are hereby incorporated by reference herein in theirentireties.

BACKGROUND OF THE INVENTION

This invention relates to medical implants for improving or modifyingthe performance of tissue structures in a patient's body such as asphincter, a tubular conduit, or an organ. An illustrative use of theinvention is improving the performance of a patient's lower esophagealsphincter (“LES”) as a treatment for gastro-esophageal reflux disorderor disease (“GERD”). However, this is only an example of how theinvention may be used, and many other uses will be readily apparent tothose skilled in the art. To list just a few further examples, theinvention may be applied to other sphincters in the body such assphincters in the urinary tract and elsewhere in the digestive tract.The apparatus of the invention may be used around the stomach as part ofa treatment for obesity.

A common cause of GERD is inadequate functioning of the LES. The LES(and perhaps some associated tissue structures) normally keeps the lowerpart of the esophagus closed in order to prevent stomach contents fromentering the esophagus. The LES opens during swallowing to allowwhatever is being swallowed to pass from the esophagus into the stomach.The LES also opens to allow excess pressure in the stomach to escape viathe esophagus. However, normal stomach pressure is substantiallyresisted by a normally functioning LES to keep the contents of thestomach from entering the esophagus. In a patient with GERD the cause isfrequently an LES that has lost its ability (strength or “tone”) toresist normal stomach pressure and prevent stomach contents from comingback into the esophagus. This can cause discomfort (“heartburn”), and ifleft untreated, can cause damage to the esophagus that can lead to veryserious adverse consequences for the patient.

It has been proposed to implant magnets in a GERD patient to improve thestrength or tone of the patient's LES. For example, two magnets may beimplanted in the esophagus on respective opposite sides of theesophageal lumen at or near the LES. Magnetic attraction between themagnets helps to hold the esophagus closed (except during swallowing orexcess stomach pressure venting) and thereby reduces or eliminates thereflux of GERD. In following this approach, it would be desirable toavoid subjecting tissue to long-term, direct pressure from the magnets,such as when tissue between two mutually attracting magnets or magneticstructures is the only thing keeping the magnets or magnetic structuresapart. Such pressure can interfere with blood flow to the tissue betweenthe magnets or magnetic structures, which can be unhealthy for thattissue. For example, tissue death (necrosis) can result.

SUMMARY OF THE INVENTION

In accordance with the invention, a medical implant includes pluralbodies, adjacent ones of which are resiliently attracted to one another(e.g., by magnetism, spring force, or the like). The bodies can bedisposed in an array (e.g., an annular array) around a body tissuestructure to be treated. The structure of the implant maintains an openarea inside the array of at least a predetermined non-zero minimum size.Tissue passing through that area may be subjected to some residualpressure, e.g., of the kind and in an amount that improves the tone of asphincter that is part of that tissue. But no part of the tissue isexposed to pressure of the kind that would be unhealthy for the tissue.If a normal body function (e.g., swallowing) causes the tissue structurepassing through the array of bodies that make up the implant orprosthesis to need to expand, those bodies can move resiliently apart toallow such enlargement of the tissue structure. Thereafter, the bodiesof the prosthesis move resiliently back toward one another again to helpthe tissue structure contract to its first-mentioned condition. However,this contraction of the prosthesis is limited by the prosthesis itselfto always leave open at least the above-mentioned non-zero minimum areabounded by the prosthesis. The contracting prosthesis may not alwaysreach the above-mentioned limit, if the prosthesis is sized or designedto apply some residual pressure to the tissue. But if that is the case,the residual pressure is small enough (e.g., it is the result of arelatively small force distributed over a relatively large area oftissue) so that it is not a problem for the tissue even if appliedlong-term.

Other aspects of the invention relate to methods for implanting aprosthesis in a patient in accordance with the invention. For example,an implant in accordance with the invention may be introduced into thepatient in a substantially linear array. The array may be wrapped aroundthe outside of the target body tissue structure. Opposite ends of thearray may be joined to one another to form a closed loop around thetarget body tissue structure. These steps may be performed in any of anumber of ways. For example, the implanting may be done surgically. Asanother example, the implanting may be done laparoscopically. As stillanother example, the prosthesis may be delivered into the patient via abody conduit of the patient, may then exit from that conduit at alocation interior to the patient, and may then be implanted at theintended site using instrumentation that accompanies or follows theprosthesis into the patient via the conduit and out of that conduit atthe interior location. As a specific example of the last-mentionedpossibility, the prosthesis may be delivered into the patient in alinear condition via the patient's mouth and esophagus and into thestomach. The prosthesis may then exit through a temporary aperture inthe side wall of the stomach and thereby enter the extra-luminal space.The prosthesis may then be secured around the external esophagus orupper stomach.

Further features of the invention, its nature and various advantageswill be more apparent from the accompanying drawings and the followingdetailed description of the preferred embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified elevational view of an illustrative embodiment ofprosthetic implant apparatus in accordance with the invention.

FIG. 2 is a simplified perspective view of apparatus of the type shownin FIG. 1 implanted and functioning in a patient in accordance with theinvention.

FIG. 3 is a simplified sectional view of apparatus of the type shown inFIG. 1.

FIG. 4 is similar to FIG. 1, but shows another operating condition ofthe apparatus.

FIG. 5 is an enlargement of a representative portion of what is shown inFIG. 3.

FIG. 6 is another view similar to FIG. 2, but shows another operatingcondition of the apparatus.

FIG. 7 is a graph that is useful in explaining certain aspects of theinvention.

FIG. 8 is another graph that is useful in explaining certain aspects ofthe invention.

FIG. 9 is a simplified sectional view of a portion of a patient'sanatomy.

FIG. 10 is similar to a portion of FIG. 9 showing illustrative treatmentof the patient's anatomy in accordance with the invention.

FIG. 11 is a simplified sectional view of a representative portion ofanother illustrative embodiment of prosthetic implant apparatus inaccordance with the invention.

FIG. 12 is similar to FIG. 6 for an embodiment of the type shown in FIG.11.

FIG. 13 is similar to FIG. 12, but shows yet another illustrativeembodiment of prosthetic implant apparatus in accordance with theinvention.

FIG. 14 is similar to FIG. 11 for an embodiment of the type shown inFIG. 13.

FIG. 15 is a simplified elevational view of a representative portion ofstill another illustrative embodiment of prosthetic implant apparatus inaccordance with the invention.

FIG. 16 is a simplified elevational view of one of the components shownin FIG. 15 in another condition of that component.

FIG. 17 is similar to FIG. 15, but shows another operating condition ofthe apparatus.

FIG. 18 is another graph that is useful in explaining certain aspects ofthe invention.

FIG. 19 is a simplified elevational view of a representative portion ofyet another illustrative embodiment of prosthetic implant apparatus inaccordance with the invention.

FIG. 20 is similar to FIG. 19, but shows another operating condition ofthe apparatus.

FIG. 21 is a simplified elevational view showing use of still anotherillustrative embodiment of prosthetic implant apparatus in accordancewith the invention.

FIG. 22 is a simplified cross sectional view of what is shown in FIG.21.

FIG. 23 is similar to FIG. 22, but shows another operating condition ofthe apparatus.

FIG. 24 is a simplified perspective of portions of prosthetic implantapparatus like that shown in FIGS. 21-23.

FIG. 25 is similar to FIG. 23 for yet another illustrative embodiment ofprosthetic implant apparatus in accordance with the invention.

FIG. 26 is similar to FIG. 25, but shows another operating condition ofthe apparatus.

FIG. 27 is similar to FIG. 25 for still another illustrative embodimentof prosthetic implant apparatus in accordance with the invention.

FIG. 28 is similar to FIG. 27, but shows another operating condition ofthe apparatus.

FIG. 29 is generally similar to FIG. 5 for another illustrativeembodiment of the invention.

DETAILED DESCRIPTION

As shown in FIG. 1, an illustrative embodiment of apparatus 10 inaccordance with the invention includes a plurality of substantiallycylindrical bodies or “beads” 20. Beads 20 can be formed into a closedloop with an open interior as shown in FIG. 1. Beads 20 are strungtogether by links 30. In general, each bead 20 has a link 30 to each ofthe immediately adjacent beads on each side of the first-mentioned bead.The possible exception to this is for the linkage between the tworight-most beads in FIG. 1. Each of these beads has a link eyelet 40extending outwardly from the bead toward the other of these beads. Linkeyelets 40 may initially be separate from one another (e.g., as shown inFIG. 2 or FIG. 4). This allows apparatus 10 to (at least initially) notform a closed loop, which non-loop condition may be helpful in initiallyimplanting the apparatus in a patient. If and when desired, link eyelets40 may be connected to one another (e.g., by tying them together with astrand of suture material). For example, FIG. 2 shows apparatus 10implanted annularly and coaxially around the outside of a patient'sesophagus 50. Although FIG. 2 does not show a connection between linkeyelets 40, it will be apparent that such a connection can be made(e.g., with suture material). As will be seen, links 30/40 are importantto controlling the position of each bead 20 and for allowing diameterincreases of the prosthesis.

Each bead 20 in apparatus 10 is resiliently attracted to the adjacentbeads in the string or loop. This resilient attraction may be providedby means such as magnetic force, spring force, or the like. Use ofmagnetic force will be described first. Other examples will be describedlater.

FIGS. 3-5 show an example in which magnetic force is used to attractadjacent beads 20 to one another. Each bead 20 includes two matinghousing components 60 and 70. Each housing component 60 or 70 isbasically cup-shaped. Each housing component 60 has a hollow post 62standing up from the center of its bottom. The part of each post 62 thatis most remote from the remainder of cup 60 extends into an aperture inthe bottom of the associated cup 70. The lips of the cups 60 and 70 thatform a bead 20 abut one another annularly around the bead. Thus theinteriors of the cups 60 and 70 of a bead 20 form a hollow annular spaceinside the bead and concentrically around the post 62 inside the bead.One or more toroidal permanent magnets 80 are concentrically disposedabout post 62 in this space. Magnets 80 are magnetically polarized sothat the magnets in adjacent beads 20 in the string or loop magneticallyattract one another. (See FIG. 5 in which the polarity of each magnet 80is indicated by the letters N and S.) This magnetic attractionresiliently attracts adjacent beads in the string or loop toward oneanother.

The hollow interior of each post 62 is large enough to easily andloosely accommodate end portions of two links 30 (or end portions of onelink 30 and one link eyelet 40). (Because for this purpose link eyelets40 are substantially similar to links 30, it will not be necessary toseparately mention eyelets 40 again in this immediate discussion. Itwill be understood that they are subsumed in the discussion of links30.) In each bead 20 one of the associated links 30 extends out of anaperture in the bottom of cup 60. This aperture is large enough to allowthe main length of the link 30 to pass freely through the aperture, butit is not large enough to allow an enlarged stop 32 at the end of thelink to pass through the aperture. The other link 30 associated witheach bead 20 extends out of an aperture in the center of a washer-likecap 72 that is used to substantially close an aperture in the bottom ofcup 70 and the otherwise open end of the hollow in post 62. Again, theaperture in cap 72 is large enough to allow the main length of theassociated link 30 to pass freely through, but it is not large enough toallow the enlarged stop 32 at the end of the link to pass.

The various components of apparatus 10 can be assembled (duringmanufacture) as follows. Each link 30 can be initially provided withonly one enlarged end stop 32. The other end of a link 30 can be passedsuccessively through the aperture in the bottom of a cup 60 (not yetattached to a cup 70) and the aperture in a washer-like cap 72 (also notyet attached to a cup 70). An enlarged end stop 32 can be formed on theother end of the link 30. Magnets 80 can be placed in the cup 60. A cup70 can be attached to the cup 60. A washer-like cap 72 can be attachedto the cup 70.

Magnets 80 do not need to be biocompatible because the magnets can becompletely sealed inside beads 20. The parts of apparatus 10 that willbe exposed to a patient's body are preferably biocompatible. Thesecomponents are cups 60 and 70 (including posts 62), washer-like caps 72,and links 30/40. An example of a biocompatible material that is suitablefor these components is titanium, but many other suitable metallic andnon-metallic materials are known to those skilled in art and can be usedif and as desired. Assuming that one or more metals are used forcomponents 30, 40, 60, 62, 70, and 72, enlarged end stops 32 may beformed as weld balls, annular hermetic welds may be formed between theabutting lips of cups 60 and 70, a similar annular hermetic weld may beformed between mating components 62 and 70, and spot welds may be usedto secure washer-like caps 72 to the associated cups 70. Hermeticsealing of this last connection is not required because of the hermeticsealing between components 62 and 70. Alternatively, the mating betweencomponents 62 and 70 could be left unsealed, and a seal weld could beused between component 72, on the one hand, and components 62 and 70, onthe other hand.

Note that the ends of each cylindrical bead 20 are preferablyapproximately spherical. Note also that links 30 may be somewhat bentlaterally along their lengths. Features such as these help the structureform a closed loop that can resiliently enlarge and contract withoutmechanical interference (other than the intended ultimate limits on bothenlargement and contraction as will now be described).

As has been mentioned, the magnets 80 in beads 20 resiliently attractadjacent beads into contact with one another as shown in FIGS. 1, 3, and5. However, this magnetic attraction between adjacent beads can beovercome, e.g., by sufficiently forceful radial enlargement of apatient's body tissue structure that passes through the interior of aclosed loop of the beads. For example, FIG. 2 shows beads 20 separatedfrom one another in the annular direction by temporary radialenlargement of esophagus 50 (e.g., due to swallowing of a bolus offood). FIG. 4 shows the extreme upper limit of annular enlargement ofapparatus 10. This enlargement limit is reached when each link 30/40 ispulled as far out of each bead 20 as the enlarged stops 32 on the endsof the links will permit. (It is assumed in this discussion of FIG. 4that eyelets 40 are attached to one another (e.g., by a suture knot (notshown) between them).) Annular enlargement of apparatus 10 is stopped byattainment of this condition.

At all times that apparatus 10 is annularly enlarged to any degree, itis resiliently urged to return to its fully, annularly contractedcondition by the magnetic attraction between beads 20. (Note thatapparatus 10 has its lowest force urging contraction when beads 20 areat maximum separation from one another (e.g., as shown in FIGS. 2 and4).) Annular contraction of apparatus 10 is, however, ultimately limitedby each bead 20 coming into contact with the adjacent beads in thestring or loop. This maximally contracted condition of apparatus 10 isshown, for example, in FIGS. 1, 3, and 5. (Note that apparatus 10 hasits highest force urging contraction when beads 20 are closest togetheras shown in FIGS. 1, 3, and 5.) When each bead 20 is in contact with theadjacent beads as shown in these FIGS., the apparatus itself stops orprevents any further annular contraction of the apparatus. The structureis completely stable in this condition. Beyond this point the apparatusapplies no additional pressure to the patient's body tissue structurethat passes through the interior of the apparatus. This self-stopping orself-limiting contraction of the apparatus of the invention can be animportant advantage. If the only thing resisting resilient movement oftwo (or more) bodies toward one another is tissue between the bodies,the continuous pressure of those bodies on the tissue can adverselyaffect the tissue if that pressure is sufficiently great. For example,it may cause necrosis of the tissue. This cannot happen with embodimentsof this invention (like the one being discussed) in which the apparatusitself ultimately absorbs force exerted by components of the apparatusbeyond the force that produces maximum annular contraction of theapparatus. The interior of apparatus 10 always remains open as shown inFIG. 1, even if there were no tissue in that interior.

Certain aspects of the behavior of apparatus 10 are illustrated by FIGS.7 and 8. FIG. 7 is a graph of force versus separation between two bodiesthat are magnetically attracted to one another. FIG. 7 illustrates thewell known fact that as the distance between the two objects increases,the magnetic force attracting them toward one another decreases, and thedecrease is an exponential function of the gap or spacing between thebodies.

FIG. 8 shows how the principle of FIG. 7 applies in the case ofapparatus like above-described apparatus 10. When apparatus 10 is in itsmost annularly contracted condition with each of beads 20 in contactwith the adjacent beads, the magnetic force holding apparatus 10 in thatstate of maximum contraction (or zero extension, in the terms employedin FIG. 8) is at a maximum (point A in FIG. 8). If apparatus 10 is thensubjected to at least that amount of force tending to annularly enlargeit, two of beads 20 will begin to move apart. Assuming that all of beads20 have the same magnetic attraction to their neighboring, adjacentbeads, it can be a matter of chance which two of the beads begin toseparate from one another. As soon as two beads begin to separate, theforce required to continue the separation of these two beads dropsexponentially, until maximum separation between these two beads isreached at point B in FIG. 8. Note that there is still some resilient,restorative force at point B.

If, beyond the enlargement of apparatus 10 that has occurred when pointB is reached, still more enlargement is needed, the force required toinitiate such further enlargement returns to approximately the startingforce as shown at point C. If at least such further enlargement force ispresent, two more of beads 20 will begin to separate to provide afurther annular enlargement of apparatus 10.

The above-described process of beads 20 separating from one another oneafter another will continue, following the force and displacementdiagram shown in FIG. 8, until the patient's body tissue structure thatis inside apparatus 10 has reached a size such that it no longer exertssufficient enlarging force on the apparatus to cause further enlargementof the apparatus, or until the apparatus has reached its condition ofmaximum annular enlargement.

Turning now to more detail regarding how apparatus of the type shown anddescribed above may be used as a medical implant in accordance with theinvention, an illustrative use is as a treatment for gastro-esophagealreflux disorder or disease (“GERD”). In such a condition, the bodystructures that normally function to keep the lower part of theesophagus (near the stomach) closed, except when swallowing or whenexcessive pressure in the stomach needs to be relieved via theesophagus, is no longer functioning properly or adequately. Thisstructure includes the lower esophageal sphincter (“LES”), possibly incooperation with other tissue structures where the esophagus passesthrough the diaphragm (see FIG. 9, in which the reference numbersindicate the following: esophagus 50, lumen 51, mucosa 52, muscle wall53, diaphragm 54, and stomach 55). FIG. 10 shows where the prosthesis 10of this invention may be implanted in a patient to help restore normalfunctioning to the lower part of the esophagus. In the example shown inFIG. 10, apparatus 10 is disposed in a closed loop annularly around theoutside of the esophagus between the diaphragm and the point where theesophagus enters the stomach. (Reference number 56 in FIG. 10 identifiesadditional muscle.)

Apparatus 10 can be implanted as shown, for example, in FIG. 10 in anyof several ways. Typically, during the initial part of the implantprocedure, apparatus 10 has not yet been made into a closed loop byconnecting eyelet links 40. Instead, apparatus 10 is wrapped around theesophagus with eyelets 40 unconnected. When apparatus 10 is positionedas desired, eyelets 40 may be connected to one another (e.g., with asuture knot) to form the apparatus into a closed loop. If necessary ordesirable to prevent excessive movement of apparatus 10 along the lengthof the esophagus, the apparatus may be secured (e.g., by one or moresutures, one or more clips, etc.) to the outside of the esophagus and/orto other adjacent tissue. This securement structure (e.g., sutures usedfor this purpose) may be dissolvable.

Any of several techniques can be used for introducing the implant 10into the patient. For example, this may be done using open or relativelyopen surgery. As another example, the implant may be introduced into thepatient using less invasive procedures such as laparoscopy andlaparoscopic instruments. As still another example, the implant may beintroduced trans-gastrically. In this technique the implant isintroduced trans-orally into the esophagus, passed down the esophagus,and into the stomach. A dilator device is used to penetrate the wall ofthe stomach sufficient in size to allow the implant to be passed throughthis dilator into the space outside the stomach. The device, usinginstruments such as a stylet, can then be threaded around the loweresophagus. The implant can be connected into a closed loop with asuture, a clip, or stronger magnet beads located at each end. Theimplant may be modified to use an over-the-wire technique for thisdelivery method. In this case, a guide wire is placed around the distalesophagus and the implant is threaded over this wire once the wire is inposition. The wire can then be removed.

It may be desirable to first measure or “size” the outer circumferenceof the esophagus where apparatus 10 is to be implanted. This may be doneusing one or more sizing instruments. When the desired implant size hasbeen determined, an implant of that size may be implanted. Implantshaving different sizes may be provided by, for example, producingimplants with different numbers of a given size bead 20, or by usingbeads 20 of different sizes to make implants of different sizes.

The implant may be medicated for any of several purposes. For example,such medication may include an antibiotic to combat infection, and/orthe medication may include a steroid to promote appropriate healing.

With regard to the annular size of the prosthesis, it is currentlythought desirable in the treatment of GERD, for example, to slightly“under-size” apparatus 10 for the outside of the esophageal tissuestructure to which the apparatus will be applied. This means selecting asize of prosthesis such that when the implant is in place in thepatient, there is at least some space in the annular or circumferentialdirection between two (preferably only two) of beads 20. (See FIG. 6,which is intended to illustrate this condition of apparatus 10,implanted annularly around the outside of esophagus 50.) Indeed, it isthought especially preferable for the space (G in FIG. 6) between thetwo beads 20 mentioned in the preceding sentence to be relatively closeto the maximum inter-bead spacing (i.e., the “link-length” in FIG. 8).This gives the implant an “at rest” force characteristic like that shownat or slightly to the left of point B in FIG. 8. In this way, theimplant always applies some radial or annularly compressive force to theesophagus, but this force is relatively low. This force should besufficient to significantly improve the “tone” and therefore thereflux-resisting closing of the esophagus. By thus slightly under-sizingthe implant, it is thought that the “full-time” effectiveness of theimplant in combating reflux is enhanced. However, this is only anoptional aspect of the invention that others may prefer not to employ.

Continuing with the discussion of the example of applying apparatus 10to a patient's esophagus, when the esophagus should be closed, theimplant helps to keep it closed. However, when the patient swallows(e.g., a bolus of food), the implant annularly enlarges to the necessaryextent to allow what has been swallowed down into the stomach. This mayinvolve any number of beads 20 moving away from the adjacent bead(s).After any bolus has passed the plane of the implant, the implantresiliently returns to its initial, more annularly contracted condition.The same sequence of operations occur when excessive pressure in thestomach must be relieved through the esophagus. The implant annularlyenlarges to vent the stomach, and then resiliently annularly contractsto return to its initial condition. The force exerted on the esophagusby the implant is preferably always large enough to help prevent reflux,but it is not so large as to impede swallowing or necessary venting ofthe stomach via the esophagus.

Over time, implanted apparatus 10 may become overgrown with tissue.However, this will not interfere with operation of the implant asdescribed above. Tissue over-growth as described in this paragraph maymake it possible to form the links 30 of the prosthesis from anabsorbable (e.g., suture) material such as polyglycolic acid and/orpolylactic acid. In embodiments of this type the links would degrade anddisappear over time. Once the implant is integrated to the externalesophagus and a fibrous tissue cap has conformed to at least part of thebeads, the function of the links between the beads may not be necessary.

FIGS. 11 and 12 show an alternative embodiment in which beads 120 thatcan be flatter than beads 20 are used. Each of beads 120 includes a flatpermanent magnet 180 and two parallel links 130 to each of the adjacentbeads 120. Magnets 180 are polarized (+ and −) so that the magnets inadjacent beads magnetically attract one another. FIG. 12 shows animplant 10 that includes an annular array or closed loop of beads 120disposed annularly and concentrically around the outside of esophagus50. As compared to embodiments of the type illustrated by FIG. 1, forexample, embodiments of the type illustrated by FIG. 12 may have theadvantage of operating on tissue structure 50 along an axially longerportion of that structure.

FIGS. 13 and 14 illustrate another embodiment that can be generallysimilar to the FIGS. 11 and 12 embodiment, except that in FIGS. 13 and14 each bead 220 is a cylinder that is substantially parallel to thelongitudinal axis of esophagus 50. As in

FIGS. 11 and 12, in FIGS. 13 and 14 two parallel links 230 connect eachbead 220 to each adjacent bead. Permanent magnets 280 in the beads arepolarized to resiliently attract adjacent beads 220 toward one another.As compared to flat beads 120, cylindrical beads 220 may better conformto the annular outer surface of esophagus 50.

FIGS. 15-18 illustrate an alternative embodiment in which the attractionbetween adjacent beads 320 is provided by prestressed tension springs380 between the beads. Springs 380 can be of an elastic material such asan elastic metal or an elastic polymer. Although FIGS. 15 and 17 onlyshow two representative beads 320 and the representative spring 380between those beads, it will be understood that more beads and springsare typically provided so that a closed loop of such beads (joined bysuch springs) can be formed, e.g., around the outside of a body tissuestructure such as the esophagus. In the absence of beads 320, therelaxed state of a representative spring 380 is shown in FIG. 16. Thusspring 380 must be stretched (tensioned) somewhat to enable it to reachanchor points 382 on two adjacent and mutually contacting beads 320 asshown in FIG. 15. This means that spring 380 resiliently urges adjacentbeads 320 toward one another even after those beads are in contact withone another.

From the condition shown in FIG. 15, spring 380 allows adjacent beads320 to move apart as shown, for example, in FIG. 17. Of course, asspring 380 stretches to thus allow beads 320 to move apart, the springforce urging beads 320 back toward one another increases in proportionto the spacing between the beads. This is illustrated by FIG. 18. Ascompared to the earlier-described magnetic embodiments, in which (atleast theoretically) each inter-bead gap tends to open fully beforeanother inter-bead gap begins to open, in spring embodiments asillustrated by FIGS. 15-17 all of the beads tend to move apart bysimilar amounts at the same time (assuming that all of the inter-beadsprings 380 are of approximately the same strength). FIG. 18 istherefore indicative (depending on the horizontal and vertical scalesemployed) of both the force exerted as any one spring 380 is stretchedor as the device as a whole is stretched (annularly enlarged).

Although FIGS. 15-17 show an illustrative spring embodiment in whichsprings are outside beads 320. It will be understood that springs forsuch an embodiment could instead be inside the beads. For example,prestressed compression coil springs inside the beads and aroundportions of the lengths of inter-bead links like 30, 130, or 230 inearlier FIGS. could be used to resiliently bias adjacent beads towardone another.

It will be noted that spring embodiments (e.g., as in FIGS. 15-17 or asotherwise described above) have the same advantage of self-limitingannular contraction as the earlier-described magnetic embodiments. Onceall of the adjacent beads in a closed loop of spring-connected beads arein contact with one another, the loop cannot get any smaller and theinterior of the structure inherently remains open (e.g., as in FIG. 1).

If desired, any of the above-described embodiments (including themagnetic embodiments) can be augmented to produce substantially equalspacing between adjacent beads at all times. FIGS. 19 and 20 illustratean embodiment with such augmentation. In addition to whatever inter-beadattraction is employed, interconnected parallelogram linkages 490 areused between the beads 420 in this embodiment. Two crossing links 490are pivotally connected to each bead at point 492. The ends of theselinks adjacent each next bead 320 are pivotally connected to theadjacent ends of the links 490 on that next bead at points 494. FIG. 19shows the condition of the apparatus when adjacent beads 420 are closeto or in contact with one another. FIG. 20 shows the condition of theapparatus when adjacent beads 420 are farther apart. Linkage 490/492/494keeps the spacing between the adjacent beads substantially uniform,regardless of the amount of that spacing. Moreover, this result isachieved even for magnetic attraction between adjacent beads. This giveseven a magnetic bead embodiment an overall force vs. displacementcharacteristic like that shown in FIG. 7, rather than like thecharacteristic shown in FIG. 8. (Of course, the horizontal scale in FIG.7 will be different, depending on whether the FIG. depicts separationbetween two adjacent magnetically attracted beads or overall enlargementof a multibead magnetic prosthesis.)

Assuming that FIGS. 19 and 20 show an embodiment with magnetic beads420, linkage 490/492/494 may take the place of other inter-bead linkslike 30/130/230 in earlier-depicted embodiments.

FIG. 29 shows an alternative embodiment in which the inter-bead linksare provided by a continuous element 30 of elastic material. Thiselement passes through each bead 20, and extends from bead to beadaround the annular prosthesis 10. Element 30 may initially have two freeends (e.g., in the form of loops) that can be connected to one anotherto form an annular prosthesis. Beads 20 can move apart by stretchingelement 30. Element 30 resiliently urges beads 20 to move back intocontact with one another. Element 30 is preferably somewhat prestressedeven when all of beads 20 are in contact with one another. In theembodiment shown in FIG. 29, beads 20 are not at fixed locations alongthe length of element 30. In an alternative embodiment some or all ofbeads are secured to element 30 at predetermined locations along itslength.

Another illustrative embodiment of the invention is shown in FIGS.21-23. In this embodiment two magnetic structures 520 are attached,e.g., to the outside of esophagus 50, on respective opposite sides ofthe esophagus in a common plane that is substantially perpendicular tothe longitudinal axis of the esophagus. For example, sutures 522 may beused to attach structures 520 to the esophagus. The implanted locationof structures 520 may be as shown for apparatus 10 in FIG. 10. Eachstructure 520 is arched, with the concave side of the arch facinginwardly toward the adjacent outer surface of the esophagus. Structures520 may be substantially rigid or somewhat flexible. However, ifflexibility is employed, it is preferably not so great that structures520 tend to completely lose their arched shape in use. In other words,if structures 520 are flexible, they are preferably resiliently biasedto retain arched shapes like those shown in FIG. 22.

The arc length of each structure 520 is preferably sufficient that theends of the one structure can contact the ends of the other structurebeyond esophagus 50 (i.e., with no tissue of the esophagus between thecontacting ends of the structures 520) as shown in FIG. 22. The size andamount of curvature of structures 520 is preferably sufficient to causethose structures to apply some closing pressure to esophagus 50 when theends of the structures are in contact with one another as shown in FIG.22. However, these parameters (especially the curvature) are alsopreferably sufficient to keep this FIG. 22 closing pressure on theesophagus from being too great, so as not to prevent opening of theesophagus for swallowing or normal stomach venting or to cause necroticpressure on any tissue of the esophagus. As mentioned above, each ofstructures 520 is preferably rigid enough to hold at least apredetermined minimum arched shape.

Each of structures 520 includes one or more magnets 580 for magneticallyattracting the other structure 520, e.g., across the esophagus. Thismagnetic attraction is strong enough to hold structures 520 together asshown in FIG. 22, except during swallowing or normal stomach venting.Accordingly, structures 520 are able to move apart as shown in FIG. 23when the esophageal lumen needs to enlarge for swallowing or normalstomach venting.

Like the earlier-described embodiments, embodiments of the type shown inFIGS. 21-23 have the advantage of being self-limiting as they helpesophagus 50 to close. Once the ends of structures 520 come into contactwith one another as shown in FIG. 22, they apply no excessive additionalpressure to the esophagus. A space always remains open betweenstructures 520 for esophagus 50 to pass through, with no necroticpressure being applied to any esophageal tissue between structures 520.

FIG. 24 is another view of certain components from the FIGS. 21-23embodiment. FIG. 24 shows these components without any tissue beingpresent, and also without magnets 580 in structures 520. FIG. 24 clearlyshows how structures 520 cooperate to form a passageway therebetween andthrough which a tissue structure such as an esophagus can pass.

If desired, structures 520 like those shown in FIGS. 21-24 may beadditionally or alternatively tethered to one another with thread,suture, or an elastic cord. The above-mentioned tethers may beabsorbable.

FIGS. 25 and 26 show yet another illustrative embodiment of theinvention. In this embodiment two pairs of magnets 680 are mounted sideby side on the outer surface of a flexible “belt” 620 that is disposedannularly and concentrically around the outside of esophagus 50. FIG. 25shows esophagus 50 open, and FIG. 26 shows the esophagus closed. Again,the apparatus of FIGS. 25 and 26 may be implanted as shown at 10 in FIG.10. Sutures through belt 620 and into the esophagus may be used to holdthe implanted apparatus in place.

When esophagus 50 opens as shown in FIG. 25 (e.g., for swallowing orexcess stomach pressure venting), the enlarging esophagus stretches belt620 so that the magnets 680 in one or both of the magnet pairs arepulled apart. FIG. 25 shows the magnets 680 in both pairs pulled apart,but if less opening of esophagus 50 is needed, only the magnets in onepair (i.e., the depicted upper pair or the depicted lower pair) may bepulled apart. When the esophagus can close again, the magnets 680 in thepairs go back together again as shown in FIG. 26.

The length of belt 620 between the closed magnet pairs (as in FIG. 26)is preferably selected so that the apparatus applies some additionalclosing pressure to esophagus 50, even when the esophagus is nominallyclosed. In this way the apparatus helps to prevent reflux from thestomach into the esophagus. On the other hand, no tissue is subjected toexcessive, continuous pressure, such as could produce necrosis. Forexample, no tissue is trapped between the magnets 680 in either magnetpair, and the pressure on the esophagus from belt 620 is only sufficientto help keep the esophagus closed and is not dangerous to the tissue inany way. This pressure on the closed esophagus from belt 620 is also notso large as to interfere with swallowing or venting excessive pressurefrom the stomach. In other words, the apparatus readily changes from theFIG. 26 condition to the FIG. 25 condition during swallowing or duringexcessive stomach pressure venting.

FIGS. 27 and 28 illustrate yet another embodiment. In this embodimentmore than two arcuate magnetic beads 720 are individually secured to theouter surface of esophagus 50 in an annular array that is coaxial withthe esophagus (e.g., at location 10 in FIG. 10). For example, suturesmay be used to secure each bead 720 to the outer surface of theesophagus. The beads are magnetically polarized (N/S) so that each beadmagnetically attracts its annularly adjacent neighbor beads.

When esophagus 50 is closed as shown in FIG. 28, annularly adjacentbeads 720 contact one another and form a closed loop around the outsideof the esophagus. This contact between the beads prevents any furtherannular contraction of the apparatus and thereby limits the amount ofpressure the apparatus applies to esophagus 50. As in previouslydescribed embodiments, this most-closed condition of the apparatuspreferably applies sufficient pressure to esophagus 50 to prevent refluxfrom the stomach into the esophagus. However, the attraction betweenannularly adjacent beads 720 in the most-closed (FIG. 28) condition ofthe apparatus is not so great as to prevent opening of the esophagus(e.g., as shown in FIG. 27) during swallowing or venting of excessivepressure from the stomach. When esophagus 50 opens for such purposes asswallowing or stomach venting, annularly adjacent beads 720 can separatefrom one another in the annular direction as shown in FIG. 27. When theesophagus again closes after the swallowing or stomach venting event,the magnetic attraction between annularly adjacent beads 720 helps thatesophagus-closing proceed to a reflux-preventing conclusion as shown inFIG. 28 and as described above.

Such parameters as the number of beads 720, their shape (e.g., arched),etc., help ensure that when esophagus 50 is closed (FIG. 28), theinterior of the loop of beads 720 remains open, with no strong tendencyof the loop to collapse across the esophagus and apply excessive (e.g.,necrotic) pressure to any esophageal tissue inside the loop of beads.

It will be understood that the foregoing is only illustrative of theprinciples of the invention, and that various modifications can be madeby those skilled in the art without departing from the scope of theinvention. For example, although application of the disclosed apparatusto a patient's esophagus in order to treat GERD has been given the mostdetailed attention herein, it will be understood that the invention hasmany other applications. For example, apparatus in accordance with theinvention can be used around other body conduits, chambers, and/orsphincters in a patient's body. Just a few specific examples include usein treating urinary incontinence, anal incontinence, stomach sizereduction, or as a completely artificial sphincter in the event that anatural sphincter has been removed or has wholly or largely ceased tofunction. Any of the structures shown and/or described herein as loopsmay be initially provided as open structures that are only formed intoclosed loops after placement around the target tissue structure. Thisprinciple is shown and described in detail in connection withembodiments like those illustrated by FIGS. 1-6, but it can be appliedto any embodiment of the invention. Components that are described hereinas magnets or permanent magnets do not all have to be actively magnetic.Some can be merely magnetizable (e.g., bodies of ferromagnetic materialthat are magnetically attracted to actual permanent magnets by becomingat least temporarily magnetized by the magnetic field from a nearbypermanent magnet). Of course, there must always be at least onepermanent magnet in any such system. Thus elements that are referred toherein as magnets or magnetic may be either actively magnetic orpassively magnetic (i.e., temporarily magnetizable by a magnetic fieldfrom another source).

1-31. (canceled)
 32. A medical implant, the medical implant comprising:(a) a plurality of beads, wherein each bead comprises: (i) a housingassembly defining a first hollow interior and a second hollow interiorpositioned concentrically around the first hollow interior, wherein thefirst hollow interior extends from a first aperture to a secondaperture, and (ii) at least one magnet disposed within the second hollowinterior; and (b) a plurality of links joining the beads together,wherein portions of the links are slidably disposed in correspondingfirst hollow interiors of the beads such that the plurality of beads areoperable to transition between an constricted configuration and anexpanded configuration, wherein the housing assembly of adjacent beadsin the plurality of beads are configured to abut against each other inthe constricted configuration.
 33. The medical implant of claim 32,wherein the first hollow interior is isolated from the second hollowinterior.
 34. The medical implant of claim 32, wherein the housingassembly of each bead comprises a first housing component and a secondhousing component, wherein the first housing component and the secondhousing component are configured to mate together to define the firsthollow entire and the second hollow interior.
 35. The medical implant ofclaim 34, wherein the first housing component defines the firstaperture, wherein the second housing component defines the secondaperture.
 36. The medical implant of claim 35, wherein the first housingcomponent further comprises a post, wherein the post defines the firsthollow interior.
 37. The medical implant of claim 35, wherein thehousing assembly further comprises a washer-like cap associated with thesecond aperture.
 38. The medical implant of claim 34, wherein the firsthousing component comprises a cup shape.
 39. The medical implant of 32,wherein the at least one magnet comprises a toroidal shape.
 40. Themedical implant of claim 32, wherein the first aperture is located at afirst end of the housing assembly, wherein the second aperture islocated at a second end of the housing assembly, wherein the first endcomprises a convex profile, wherein the second end comprises asubstantially flat profile.
 41. The medical implant of claim 40, whereinthe at least one magnet of each bead in the plurality of beads biasesthe plurality of beads toward the constricted configuration, wherein themedical implant is sized to bear radially inwardly against an esophagusin the constricted configuration.
 42. The medical implant of claim 32,wherein at least one link in the plurality of links defines a lateralbend.
 43. The medical implant of claim 32, wherein at least one link inthe plurality of links terminate in a first stop and a second stop onopposite ends.
 44. The medical implant of claim 43, wherein the firststop of the at least one link is contained within the first hollowinterior of a first bead, wherein the second stop of the at least onelink is contained within the first hollow interior of an adjacent bead.45. A medical implant, the medical implant comprising: (a) a pluralityof beads, wherein each bead comprises: (i) a housing assembly defining afirst hollow interior and a second hollow interior positionedconcentrically around the first hollow interior, wherein the firsthollow interior extends from a first aperture to a second aperture, and(ii) at least one magnet disposed within the second hollow interior,wherein adjacent beads in the plurality of beads are magneticallyattracted to each other; and (b) a plurality of links joining the beadstogether, wherein the plurality of links each terminate into a stophoused within the first hollow interior, wherein portions of the linksare slidably disposed in corresponding first hollow interiors of thebeads such that the plurality of beads are operable to transitionbetween an constricted configuration and an expanded configuration,wherein the stop of each link in the plurality of links is configured toabut against either the first aperture or the second aperture in theexpanded configuration.
 46. The medical implant of claim 45, wherein thehousing assembly further comprises a post defining the first hollowinterior.
 47. The medical implant of claim 45, wherein at least one linkin the plurality of links comprise an elongated lateral bend.
 48. Themedical implant of claim 45, wherein the plurality of beads areconfigured to radially expand and contract between the constrictedconfiguration and the expanded configuration.
 49. The medical implant ofclaim 45, wherein the housing assembly of adjacent beads are configuredto abut against each other in the contracted configuration.
 50. Themedical implant of claim 45, wherein the housing assembly comprises afirst cup shaped housing component and a second cup shaped housingcomponent configured to mate together.
 51. A medical implant, themedical implant comprising: (a) a plurality of beads, wherein each beadcomprises: a housing assembly defining a first hollow interior and asecond hollow interior positioned concentrically around the first hollowinterior, wherein the first hollow interior extends from a firstaperture to a second aperture, and (ii) at least one magnet disposedwithin the second hollow interior, wherein adjacent bead in theplurality of beads are magnetically attracted to each other; and (b) aplurality of links joining the beads together, wherein the plurality oflinks each terminated into a stop housed within the first hollowinterior, wherein portions of the links are slidably disposed incorresponding first hollow interiors of the beads such that theplurality of beads are operable to transition between an constrictedconfiguration and an expanded configuration, wherein the housingassembly of adjacent beads in the plurality of beads are configured toabut against each other in the constricted configuration, wherein thestop of each link in the plurality of links is configured to abutagainst either the first aperture or the second aperture in the expandedconfiguration.